1. Field of the Invention
This invention relates to the manufacture of electronic modules, namely flip chip packaging, utilizing an improved method of assembling the module. The improved method provides enhanced adhesion between a chip and a substrate by treating the passivation coating of the chip. The result is a more robust electronic module.
2. Description of Related Art
Typically, in flip chip packaging, one or more integrated circuit chips are mounted on a substrate to comprise the electronic module. Pads on the chip are electrically and mechanically connected to corresponding pads on the substrate by a plurality of electrical connections such as solder joints. The chip and substrate are then subjected to a higher temperature causing the solder to melt and wet each pad in the module. The assembly is cooled causing the solder to solidify, thereby providing one or more electrical connections between the chip and the substrate to form the electronic module.
Subsequently, the module may receive a nonconductive underfill to reduce the fatigue of the solder joints, provide better adhesion between the chip and the substrate, and protect the module from contaminants. In underfilling the electronic module, a polymer, typically an epoxy resin, with ceramic or glass filler, is allowed to flow under the chip, between the solder joints, and heated at an elevated temperature to cure the underfill material.
However, it is difficult to promote adhesion between the chip and the underfill material. A layer of passivation on the chip once cured is substantially inert. Thus, it would be desirable to treat the cured passivation of the chip such that it is reactive and will bond to the underfill material.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a robust electronic module having enhanced adhesion between the chip and substrate.
It is another object of the present invention to provide a method of assembling a robust electronic module having enhanced adhesion between the chip and substrate.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.